Download Name MEASURING AND USING ELECTRICITY from the series

Name ____________________
MEASURING AND USING ELECTRICITY
from the series Electricity and Magnetism
Electric power is the amount of electric energy that flows through a circuit in a
given amount of time. Electric power is measured in units called watts. The
amount of wattage used by an electrical device is determined by multiplying the
voltage of the circuit times the current. The current is measured in amperes. Here
is a formula for calculating electric power.
Power = voltage x current (amps)
EXAMPLE: A hair dryer needs 10 amperes of current in a 120-volt circuit. How
much power does it use?
SOLUTION: Power = voltage x current
120 volts x 10 amps = 1,200 watts
The hair dryer uses 1,200 watts of power every hour.
A kilowatt is used to measure large amounts of electrical power. A kilowatt is
equal to 1,000 watts, so the hair dryer uses 1,200 watts or 1.2 kilowatts of power.
Directions: Try these problems using the information and formula from the
top part of this sheet. (Give your answers in watts or kilowatts.)
1. A washing machine uses six amperes of current in a 120-volt circuit. How
much power does it use?
2. A color television needs to be plugged into a 120-volt circuit. It uses 2.5
amperes. What is the television’s wattage?
3. The wattage of a vacuum cleaner is calculated to be 1,080 watts. If it is in a
120-volt circuit, how many amperes of current does the vacuum cleaner draw?
4. A clothes dryer has a wattage of 2.4 kilowatts. If it is in a 120-volt circuit, what
is the amperes it needs to run?
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